1. Field of the Invention
This invention relates to a process for pretreating biomasses in advance of their enzymatic treatment. More particularly it relates to a process for pretreating biomasses in advance of their enzymatic treatment which comprises treating a mixture of a biomass with an aqueous solution of alkaline compounds by means of a biaxial extruder.
2. Description of the Prior Art
Since the oil crisis in the year 1974 i.e. the so-called primary oil shock, review of various substitute resources and technical development for utilizing the resources have been advanced in order to avoid excessive dependency on fossil resources. Among the resources, biomasses have been particularly noted as reproducible resources, and techniques for utilizing them have been studied. Cellulose as a main component of biomasses is enzymatically or chemically decomposed into glucose which is fermentatively converted into ethanol which is, in turn, used as liquid fuels or chemical raw materials. Enzymolysis process of cellulose has such advantages that the process can be carried out under milder conditions than those in chemical decomposition process, complicated apparatus is unnecessary, etc. but the process also has the following drawbacks: (1) raw material biomasses, as they are, are difficult to be subject to the action of cellulase enzyme; (2) the reaction is slow; (3) a considerable cost is needed for enzyme preparation and its recovery and reuse are difficult; etc. As for the pretreatment process of biomasses in advance of their enzymolysis, fine-grinding treatment, alkali-cooking treatment, etc. have so far been known, but these treatments are not practical so much since any of them needs a considerable cost and treating time. Among them, Japanese patent applications Sho 56-80,998/1981 and Sho 56-80,999/1981 (Japanese patent application laid-open Nos. Sho 57-198094/1982 and Sho 57-198095/1982) (hereinafter referred to as prior inventions) are directed to substantially a combination of fine-grinding treatment with alkali-cooking treatment, and the treating time is as short as e.g. 0.25 to 4.0 hours and the percentage enzymolysis of the pretreated materials is as superior as e.g. 86.1 to 96.4 %. However, the pretreated materials of the prior inventions have been still insufficient in that even if the percentage enzymolysis is high, the treating time is long. Thus, the present inventors have made extensive research on the pretreatment process for decomposing biomasses by means of cellulase enzyme, and have succeeded in a continuous pretreatment of biomasses by means of a biaxial extruder.